**3. Genes associated with SLE**

Genes associated with lupus include genes of the HLA of the MHC group of genes and non-HLA genes such as interferon genes, autophagy genes and the X-linked group genes and others. Among them, the HLA genes are those that play the most important role in the pathogenesis of lupus erythematosus. The different groups of these genes will be discussed in detail below [5].

## **4. HLA genes of the MHC and lupus**

The human MHC genes are located in a segment of chromosome 6 (6p21.3) that consists of three areas (I, II and III) encoding three major classes of proteins: class I human leukocyte antigens, HLA divided into antigens (A, B and Cw), HLA class II (DP, DQ and DR) and class III whose components are complement, tumor necrosis factor (TNFa) and heat shock proteins. The HLA genes were the first to be associated with SLE and this since 1970. Studies in the past have identified HLA A1, B8 – a weak association in some studies with other studies showing no association at all -DR2, DR3, DQW1, DRW52, C4 null ancestral haplotypes as susceptibility genes for lupus erythematosus. HLA DR2 has been found in 75% of white patients with SLE (normal subjects 24%), 75% are positive for DR3 (normal subjects 25%), 75% are positive for DQW1 (normal subjects 55%) and 65% haveDRW52 (normal subjects 46%) [6]. Data suggest that the HLA-D region is exerting its effect on certain autoantibody responses in lupus erythematosus. Recently, the DRB1 gene polymorphisms have been associated with different sub-groups of systemic lupus erythematosus.

Different groups of SLE are defined by autoantibodies status, HLA-DRB1 polymorphisms, immunological and clinical manifestations.

Recent research has identified four different groups described below:

